The document discusses Docker networks and provides details about the default networks that are automatically created when Docker is installed. There are three default networks: bridge, none, and host. The bridge network represents the docker0 network and is the default network that containers are connected to. The none network adds containers without a network interface, and the host network gives containers the same network stack as the Docker host. The default bridge network uses IP address 172.17.0.1/16 and connects newly launched containers to it.

1. Presentation By:
Mohammadreza Amini
Amir Arsalan
Spring 2016
IRAN OpenStack Users Group
Docker Networks

2. Agenda
Docker Networks
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The basics of Docker networking
Default Networks
Three Networks
Bridge
None
Host
The default bridge network in detail

3. Docker Networks
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The basics of Docker networking

4. The basics of Docker networking
The basic network primitive in Docker is an Ethernet bridge called "docker0."
When Docker boots up on a Linux server, it creates a default docker0 bridge
inside the Linux kernel, and docker0 creates a virtual subnet on the Docker
host. It can pass packets back and forth between containers on that host.
Docker Networks
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5. Docker Networks
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Default Networks

6. Default Network
When you install Docker, it creates three networks automatically. You can list
these networks using the docker network ls command:
$ docker network ls
NETWORK ID NAME DRIVER
7fca4eb8c647 bridge bridge
9f904ee27bf5 none null
cf03ee007fb4 host host
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7. Three networks
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Historically, these three networks are part of Docker’s implementation.
When you run a container you can use the --net flag to specify which
network you want to run a container on. These three networks are still
available to you.
●
Bridge
●
None
●
Host

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Bridge

9. Bridge
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The bridge network represents the docker0 network present in all Docker
installations. Unless you specify otherwise with the docker run
--net=<NETWORK> option, the Docker daemon connects containers to this
network by default.

10. Bridge
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You can see this bridge as part of a host’s network stack by using the
ifconfig command on the host.
$ ifconfig
docker0 Link encap:Ethernet HWaddr 02:42:47:bc:3a:eb
inet addr:172.17.0.1 Bcast:0.0.0.0 Mask:255.255.0.0
inet6 addr: fe80::42:47ff:febc:3aeb/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:9001 Metric:1
RX packets:17 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1100 (1.1 KB) TX bytes:648 (648.0 B)

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None

12. None
The none network adds a container to a container-specific network stack. That
container lacks a network interface. Attaching to such a container and looking
at it’s stack you see this:
$ docker attach nonenetcontainer
root@0cb243cd1293:/# cat /etc/hosts
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
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13. Docker Networks
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root@0cb243cd1293:/# ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
root@0cb243cd1293:/#

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Host

15. Docker Networks
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Host
The host network adds a container on the hosts network stack. You’ll
find the network configuration inside the container is identical to the
host.

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The default bridge network in detail

17. Docker Networks
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The default bridge network in detail
The default bridge network is present on all Docker hosts. The docker
network inspect command returns information about a network:

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The default bridge network in detail
$ docker network inspect bridge
[
{
"Name": "bridge",
"Id": "f7ab26d71dbd6f557852c7156ae0574bbf62c42f539b50c8ebde0f728a253b6f",
"Scope": "local",
"Driver": "bridge",
"IPAM": {
"Driver": "default",
"Config": [
{
"Subnet": "172.17.0.1/16",
"Gateway": "172.17.0.1"
}
]
},
"Containers": {},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "9001"
}

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The default bridge network in detail
The Engine automatically creates a Subnet and Gateway to the network. The
docker run command automatically adds new containers to this network.
$ docker run -itd --name=container1 busybox
3386a527aa08b37ea9232cbcace2d2458d49f44bb05a6b775fba7ddd40d8f9
2c
$ docker run -itd --name=container2 busybox
94447ca479852d29aeddca75c28f7104df3c3196d7b6d83061879e33994680
5c

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The default bridge network in detail
Inspecting the bridge network again after starting two containers shows
both newly launched containers in the network. Their ids show up in the
container

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The default bridge network in detail
$ docker network inspect bridge
{[
{
"Name": "bridge",
"Id":
"f7ab26d71dbd6f557852c7156ae0574bbf62c42f539b50c8ebde0f728a253b6f",
"Scope": "local",
"Driver": "bridge",
"IPAM": {
"Driver": "default",
"Config": [
{
"Subnet": "172.17.0.1/16",
"Gateway": "172.17.0.1"
}
]
},

22. Docker Networks
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The default bridge network in detail
"Containers": {
"3386a527aa08b37ea9232cbcace2d2458d49f44bb05a6b775fba7ddd40d8f92c": {
"EndpointID":
"647c12443e91faf0fd508b6edfe59c30b642abb60dfab890b4bdccee38750bc1",
"MacAddress": "02:42:ac:11:00:02",
"IPv4Address": "172.17.0.2/16",
"IPv6Address": ""
},
"94447ca479852d29aeddca75c28f7104df3c3196d7b6d83061879e339946805c": {
"EndpointID":
"b047d090f446ac49747d3c37d63e4307be745876db7f0ceef7b311cbba615f48",
"MacAddress": "02:42:ac:11:00:03",
"IPv4Address": "172.17.0.3/16",
"IPv6Address": ""
}
}

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The docker network inspect command above shows all the connected
containers and their network resources on a given network. Containers in
this default network are able to communicate with each other using IP
addresses

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Any Question?

25. Docker Network
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26. Docker Networks
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Mohammadreza Amini
Linux/Docker Administrator
Mohammadreza@openstack.ir
Amir Arsalan
Python Developer
Arsalan@openstack.ir
Thank You